Global positioning of a sensor with respect to different tiles for a global three-dimensional surface reconstruction

ABSTRACT

A measuring system can three-dimensionally reconstruct surface geometry of an object by, from a first pose with a sensor, generating a first three-dimensional representation of a first portion of the object, and with a first camera, generating a first image covering at least part of the first portion, and from a second pose with the sensor, generating a second three-dimensional representation of a second portion of the object, and with the first camera, generating a second image covering at least part of the second portion. A stationary first projector can be arranged externally configured for projecting a texture onto both first and second portions of the object. A stitching computer can be configured for generating a unitary three-dimensional representation of both the first and second portions of the object from the first and second three-dimensional representations based on the first and second images.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to European Patent Application No.17193340.1 filed on Sep. 26, 2017, which is incorporated herein byreference.

FIELD OF THE INVENTION

The present invention relates to a measuring system forthree-dimensionally reconstructing a surface geometry of an object.

BACKGROUND

For generating a numerical representation of a structure with athree-dimensional measurement of said structure, a variety of measuringdevices are available, such as white light scanners, blue lightscanners, optical or tactile Coordinate Measuring Machines (CMM), 3Dlaser scanners, ultrasonic thickness testers, or Computer Tomographybased scanning devices. Such devices are utilised in engineering,inspecting, and manufacturing processes in automotive and othermanufacturing industries. In these fields of application, measurementsystems are required to be flexible at use while complying with highestprecision standards.

Generic measuring devices can also merge several partial measurements(i.e. measurements of parts of the object) for generating acomprehensive three-dimensional representation of a structure. Due tothis functionality, which is also referred to as stitching, a structurecan be divided into sections (i.e. into tiles) of which partialmeasurements are taken.

In the stitching process, the relative position(s) and orientation(s)(i.e. the relative pose(s)) between the point clouds of the particulartiles need to be determined. For this purpose, known measuring devicesare reliant on mechanisms for detecting the pose of the measuring deviceover the time, so as to derive said relative poses of the tiles. Forexample, the pose of the measuring device is monitored by angle encodersof a robot arm and/or by laser tracking of the measuring device.

These pose detection mechanisms are however subject to an accumulationof errors, to temperature dependency, and/or to a disadvantageousrepeatability. Therefore, said mechanisms need a calibration at regularintervals in order to provide a sustainable precision when stitching thetiles. These circumstances cause time expenses in the measurementprocess and still provide a relatively unstable precision regarding thetile poses.

Furthermore, for positioning, other known measuring systems rely on theusage of targets/markers on the part, which are captured from differentviewing points and therefore act as reference. This, however, is notonly expensive but also a complex endeavor.

SUMMARY

In some embodiments, the invention provides a measuring system providingan improved stitching functionality. In particular, the presentinvention provides a measuring system with a higher and more stableprecision regarding the stitching of tiles. Another embodiment of theinvention is to make the measurement process less complex.

In some embodiments, at least one of these improvements is achieved bythe measuring system according to embodiments described herein.

In some embodiments, the invention relates to a measuring systemconfigured for three-dimensionally reconstructing a surface geometry ofan object, the system comprising a movable measuring device comprising asensor and a first camera, wherein the measuring device is configuredfor, from a first pose with the sensor, generating a firstthree-dimensional representation of a first portion of the object, andwith the first camera, generating a first image covering at least partof the first portion of the object, and from a second pose with thesensor, generating a second three-dimensional representation of a secondportion of the object, and with the first camera, generating a secondimage covering at least part of the second portion of the object, astationary first projector arranged externally with respect to themeasuring device, and configured for projecting a texture onto bothfirst and second portions of the object, and a stitching computerconfigured for generating a unitary three-dimensional representation ofboth the first and second portions of the object from the first andsecond three-dimensional representations based on the first and secondimages.

In some embodiments, the sensor is configured for generatingthree-dimensional representation. The sensor may comprise at least onecamera, in particular a stereo camera. The sensor may, in particular,comprise the first camera and a second camera.

The sensor, however, may alternatively or additionally comprise anElectronic Distance Meter (EDM). The sensor may alternatively oradditionally comprise a laser scanner.

In some embodiments, the texture may have a non-repetitive pattern. Inother words, the projector may be configured for projecting the texturewith a non-repetitive pattern.

In some embodiments, the first projector may be configured forprojecting the same texture with respect to the moments the first camerais generating the first and second image.

For generating a unitary three-dimensional representation, the stitchingcomputer may be configured for matching the first and secondthree-dimensional representations based on the texture as captured inthe first and second images.

The first image, the second image, the first three-dimensionalrepresentation, and the second three-dimensional representations mayhave a common overlap area. That is, the first pose and the second poseare chosen accordingly to this end.

In some embodiments, it is possible the camera has a smaller, a larger,or essentially the same field of view compared to the field of view ofthe sensor. The field of view of the camera and the field of view of thesensor, however, generally do overlap at least in part due to theirsetup. In other words: the first image and the first three-dimensionalrepresentation have a common (first) overlap area. This first overlaparea, again, has an overlap with a second overlap area (which is anoverlap of a second image with a second three-dimensionalrepresentation).

For generating a unitary three-dimensional representation, the stitchingcomputer may be configured for transforming at least one of the firstand second three-dimensional representations based on matching thetexture as captured in the first image and the texture as captured inthe second image.

In some embodiments, the measuring device may further be configured for,from a third pose, with the sensor, generating a third three-dimensionalrepresentation of a third portion of the object, and with the firstcamera, generating a third image covering at least part of the thirdportion of the object, and wherein the stitching computer may beconfigured for generating a unitary three-dimensional representation ofthe first, second, and third portions of the object from the first,second, and third three-dimensional representations based on the thirdimage and at least one of the first and second image. That is, based onthe second and third images, the third three-dimensional representationis stitched with the already stitched first and second three-dimensionalrepresentation. Like this the unitary three-dimensional representationis added tile for tile.

In some embodiments, the stitching computer may be configured forapplying an Expectation-maximisation (EM)-optimisation of the unitarythree-dimensional representation of the first, second, and thirdportions of the object based on the first, second, and third images.

In some embodiments, the stitching computer may be configured forstitching the three-dimensional representations in a batch process aftera plurality of images and corresponding three-dimensionalrepresentations have been obtained.

In some embodiments, the stitching computer may be configured forreceiving pose data, wherein the pose data represent a chronologicalsequence of poses of the measuring device, and generating the unitarythree-dimensional representation based on the pose data. The pose datamay be provided by an Inertial Measuring Unit (IMU) comprised by themeasuring device, by angle encoders of a robot arm the measuring devicemay be arranged on, by an angle encoder of a turntable the measuringdevice may be arranged on, by a positioning unit of an assembly line theobject may be arranged on. The pose data are consider a rough estimation(or a means for the purpose to derive a rough estimation) of therelative pose between the three-dimensional representations of thetiles. The high-precision stitching based on the images is consideredthe fine-adjustment of the matching of the tile representations.

In some embodiments, the measuring device may be configured forgenerating the pose data. For example, the pose data may be generated byfeature tracking of a video capture by the camera. The pose data mayalso be derived by a Simultaneous Localisation and Mapping(SLAM)-process performed with the camera. Also, the pose data mayroughly be extracted by analysing the texture by its unique patternwhich is pre-known.

In some embodiments, the measuring system may further comprisepositioning means configured for moving the measuring device, and acontroller configured for controlling the positioning means andproviding the first and second pose as a predetermined pose.

In this configuration, a suitable and/or optimal pose composition may bedetermined or predefined with regard to stitching and/or capturing thethree-dimensional representations.

In some embodiments, the measuring system may further comprise a secondprojector, which is stationary or comprised by the measuring device. Thesecond projector may be configured for projecting a texture onto bothfirst and second portions of the object. In particular, the textureprojected by the second projector may differ from the texture projectedby the first projector. However, all projectors may as well project theexact same texture, wherein each projection is either processedseparately, or even if more than one projection are processed together,each projection may be projected in different areas of the part suchthat the projections do not overlap by means of their patterns.

In some embodiments, the stitching computer may be configured forscaling the three-dimensional representations by detecting andidentifying a known marker in at least one of the first image and thesecond image. In particular, several markers can be used which areplaced in different areas of the fixture. Said markers are usuallydetected in separate images and they are detected in some of the tiles.Said marker(s) may be part of the measuring system and placed at (a)defined location(s) with respect to the object. Because the pose and thedimensions of the marker(s) are predefined, the scale of thethree-dimensional representations can be derived.

In some embodiments, the first camera is arranged in a defined poserelative to the sensor.

In some embodiments, the projector illuminates constantly its textureonto the object, or the illumination is synchronised with the capturingtime points of the measuring device.

In some embodiments, the projected texture can be used to guide thesensor to a next tile. For this purpose, the texture can be coded with adefined code pattern such that the sensor can immediately read the nexttile to capture. Alternatively, the texture has a random pattern and thesensor is configured for automatically calculating the next tile tocapture. A next tile can however also be picked arbitrarily by the userunless there is no positioning initial guess. The user can even take anew tile that has no overlapping at all with other tiles and later addthe overlapping tiles inbetween. In case there is no initial guess (e.g.when the texture is not coded) the sensor can be configured forautomatically calculating the next tile to capture.

For stitching the first and second portions (tiles) of the object, thestitching computer may first apply Homography image processing to thefirst and second images, in particular in order to ease an imagecorrelation/correspondence within the images. The Homography is used totransform the images so they will be in similar viewing angles beforethe correspondence begins.

In some embodiments, rather than using a laser tracker, mapped targets,or robot repeatability, the position of a sensor is determined with oneor more digital projectors. The projector(s) projects a random textureon the part which texture is detectable by the sensor in variouspositions and orientations. The texture may be a non-repeatable patternthat ensures in each small area of it to have changes (gradients) inboth X/Y axes to enable accurate correspondence between two differentviewing points.

For this purpose, the sensor has at least one camera that captures theprojected texture. The projector(s) is/are static relative to the partduring the measurement period (in case of an automatic station with arobot, the projector should be static only along one automatic run whichtypically takes several minutes). The three-dimensional reconstructionsgenerated by the sensor have a known and pre-defined spatialrelationship with the images generated by the camera. On eachoverlapping area that is viewed from two different viewing points (ortiles), corresponding two-dimensional points in the images captured withthe camera are identified. In consequence, the correspondingthree-dimensional representations (point clouds) undergo a relativesix-degree-of-freedom transformation (rotation and translation) based onthe matched two-dimensional points in the images. To improve the finalpositioning from all pairs, optionally an EM-optimisation can be appliedthat considers all data from all 3D-2D-pairs (point clouds+images)together. The images captured from the different poses may have at leastone, i.e. in particular several overlapping areas among each other.After all tiles are stitched together, optionally a final alignment canbe applied to the resulting (CAD) model.

For matching each tile to its overlapping tiles, a rough initialpositioning may be performed at first. This optional measure canpostpone the relatively heavy calculations of correspondences betweenthe current tiles to all other tiles which most of them usually do nothave overlap with the current tile anyway. Another advantage of thismeasure is that after finding the overlapping tiles the correspondencescan be determined faster and more accurate based on the initial relativetransformation.

For example, on an automatic station with a robot, rough robot positionscan be used to obtain an initial positioning guess. These robotpositions are usually much less accurate than the required positioningaccuracy.

In another example, to obtain an initial guess on a portable\manualsystem, at least one of the following measures can be taken:

-   -   The random texture may comprise or consist of unique signatures        having markers or special codes (like QR codes or any other        detectable coded markers) that are spread all over the texture        and can be recognised in each tile. After recognising the        patterns\codes it can be checked where they appear on the        previous tiles to get a rough positioning.    -   A known path for the measuring device can be used. Such path can        be defined by the user or by the software application wherein        certain poses along the path are pre-defined and each tile is to        be taken in said poses. For example, it can be predetermined        that a subsequent tile should be captured in a certain direction        relative to the previous tile.    -   A rough tracking unit can be used on the measuring device, such        as an IMU, which gives a rough positioning used for the initial        guess.

In some embodiments, the object to be measured is arranged on a turntable or other moving platform allowing the object to be measured frommore than one position. For example, this setup can be used to measure apart (such as a fender or car door) from both sides. In this case, theunified point clouds generated from the different perspectives(stations) can be linked by relative pose data which can be obtained byat least one of the following measures:

-   -   Targets/markers can be used on the movable part fixture around        the part (not on the part). These targets/markers can be        captured and detected on tiles near the part edges that comprise        both the part and the respective target/marker. At least one        target can be detected in each station (perspective) and their        pose will be used to connect the different stations, by either a        photogrammetry mapping of several targets around the part, or by        connecting tiles from different stations that see the same        targets in the stations overlapping areas. The targets can also        be used for updating a hand-eye calibration between the robot        coordinate system and the sensor coordinate system, which is        used for calculating the initial guess positioning in automatic        systems.    -   Different stations can also be connected in the same way as        tiles are connected within the same station by using        correspondences on the projected texture on overlapping areas        between stations. In case the projector is not static relative        to the rotating table, or in case said overlapping areas are not        coverable by the projector, alternatively a physical texture        (e.g. printed) can be used.

In some embodiments, for verifying the projector did not move during ameasurement one or more tiles can be measured which cover an area withboth the projected texture and a target/marker that can be detectedregardless of the projected texture to verify the relative position ofthe projected texture and the targets has not changed even if a robotdid not arrive exactly to the same position.

In some embodiments, offline programming can help finding therecommended poses of the sensor to ensure enough overlapping between alltiles. The software can also recommend better viewing angles, e.g. alsoconsidering the projector(s) location(s) to prevent from the sensor tohide the projection.

In some embodiments, in case there is no overlapping between differentgroups of tiles the stitching of each group can be combined with otherpositioning methods of each group. In other words, each group position(one common transformation between all tiles in the group to the globalcoordinate system which is common to all groups) will be set by robotrepeatability/fixture targets/other positioning methods but the innerstitching will be done with the external projector. The tiles order isindependent on the overlapping. Two non-overlapped tiles can be takenand then the tile in between can be completed afterwards.

In some embodiments, in case there is more than one projector, imagescan be generated which cover both textures together, or images can begenerated which cover each projector texture separately to thendetermine correspondences to other tiles on each projector imageseparately. However, finally best transformation is determinedconsidering all projector images. Each projector can also be controlledseparately in each tile to define the intensity and exposure time of theprojector and the camera that takes the images.

In some embodiments, for compensating on sensor vibrations or cameravibrations, the external projector images can be generated more thanonce, for example at the beginning and at the end of generating thethree-dimensional representations (and in particular also in themiddle). Finally, the several grabs can be used for either disqualifyingthe tile if the optical sensor was not stable on the current tile, orfor calculating an average transformation combined by the relevant setof external projector images (two or more).

In some embodiments, scale can be set by the sensor three-dimensionalreconstruction. There is an option to update the scale of the sensorusing fixture targets which are mapped by photogrammetry in case themapping scale is more accurate, usually for larger scenes. At the end ofthe measurement of the part together with the fixture targets, best fitcan be determined with scale as an unknown and the scale correction canbe calculated. The best fit is between the fixture targets reconstructedby the sensor and the mapping of the fixture targets which is fixed(assuming the fixture did not change since its mapping).

In some embodiments, for better correspondence between adjacent tiles,an initial positioning guess can be used, an Homography transformationcan be calculated and images can be pre-processed to make both images assimilar to each other as possible. This is mainly an option in case twoviewing angles are different (for example if the sensor is tilted by 90degrees) or when the lighting conditions are rather different betweenthe tiles.

In conclusion, some embodiments of the invention provide a newtarget-less solution for global positioning by projecting a texture on apart using at least one external fixed projector and by stitchingadjacent tiles based on the common projected texture using hundreds ofthousands of points.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, the invention will be described in detail by referringto exemplary embodiments that are accompanied by figures, in which:

FIG. 1: shows an embodiment of the measuring system according to theinvention;

FIG. 2: shows a second embodiment of the measuring system according tothe invention;

FIG. 3: shows a third embodiment of the measuring system according tothe invention;

DETAILED DESCRIPTION

FIG. 1 shows an embodiment of the measuring system 1 according to theinvention. A projector 11 is configured for projecting a texture 110onto an object 2, which is for example a door of an automobile, whereinthe object 2 is statically positioned relative to the projector 11. Ameasuring device 10 comprising a sensor 100 and a camera 101 is movablerelative to the object. By the sensor 100, the measuring device isconfigured for sensing the surface of the object tile by tile. By thismeasurement, a point cloud is generated of each tile 1001. The camera101 is in particular configured to capture the texture 110 projected onthe tile 1001.

The projector 11 is stationary with respect to its pose relative to theobject 2 at least for the time the movable measuring device hasgenerated three-dimensional representations and images of a desiredamount of portions of the object (tiles). For example, if an object isexchanged, the projector 11 could be rearranged in order to better coverthe object with the texture.

In the embodiment shown in FIG. 1, the field of view of the camera 101coincides on the object with the field of view of the sensor 100. It ishowever also possible that said fields of view do not exactly coincideon the object. For example the field of view of the camera 101 may bewider for capturing a larger area on the object than is the field ofview of the sensor 100, or vice versa.

In particular, the camera 101 may be configured to capture on the objectan area which the sensor 100 does not capture. This extended coveragemay extend at least in part around the area captured by the sensor andcan particularly be used for stitching two adjacent tiles because (atleast) the extended coverage overlaps with the image of the precedingtile.

The camera 101 can be understood as separate element comprised by themeasuring device, besides the sensor 100. It may however also beunderstood as part of the sensor 100, for example in case an essentialelement of the sensor is at least one camera. In this case, the sensor100 is configured for generating the three-dimensional representations(point clouds) and for generating the images.

For example, a unitary three-dimensional representation of the wholeobject 2 can be generated by sequentially or accumulatively stitchingtile for tile, and/or a bunch of tiles can be recorded (point clouds andimages) and the unitary three-dimensional representation is thengenerated in a batch process using the images, wherein each image hasoverlap with at least one other image.

The projector may illuminate the object permanently while all the tiles1001 are recorded, or it may illuminate the object only in moments themeasuring device is recording each tile (generating a three-dimensionalrepresentation and image). In either case, the projected texture 110 hasthe same pattern in said moments of recording such that with means ofre-identified pattern sections in the images, the point clouds can bestitched.

According to FIG. 2, the measuring device may be hand-held and/orconfigured for being hand-held. A user 3 can guide the measuring device10 along the object to point at random or pre-defined tiles and at eachtile trigger the generation of a point cloud and a corresponding image.

According to FIG. 3, the measuring device may be arranged at the end ofa robot arm 4. Said robot arm 4 may comprise motorised joints and acontrol computer for bringing the measuring device 10 in particularposes. The robot arm 4 may be stationary or configured for beingmanually or automatically moved (e.g. in an assembly line).

Although the invention is illustrated above, partly with reference tosome preferred embodiments, it must be understood that numerousmodifications and combinations of different features of the embodimentscan be made. All of these modifications lie within the scope of theappended claims.

What is claimed is:
 1. A measuring system configured forthree-dimensionally reconstructing a surface geometry of an object, thesystem comprising: a movable measuring device comprising a sensor and afirst camera, wherein the sensor comprises an Electronic Distance Meter(EDM), wherein the measuring device is configured for: from a firstpose: with the sensor, generating a first three-dimensionalrepresentation of a first portion of the object, and with the firstcamera, generating a first image covering at least part of the firstportion of the object, and from a second pose: with the sensor,generating a second three-dimensional representation of a second portionof the object, and with the first camera, generating a second imagecovering at least part of the second portion of the object, a stationaryfirst projector arranged externally with respect to the measuringdevice, and configured for projecting a texture onto both first andsecond portions of the object, and a stitching computer configured forgenerating a unitary three-dimensional representation of both the firstand second portions of the object from the first and secondthree-dimensional representations based on the first and second images,wherein the stitching computer is configured for: applying anExpectation-maximisation (EM)-optimisation of the unitarythree-dimensional representation of the first, second, and thirdportions of the object based on the first, second, and third images. 2.The measuring system according to claim 1, wherein the sensor comprisesat least one camera.
 3. A measuring system configured forthree-dimensionally reconstructing a surface geometry of an object, thesystem comprising: a movable measuring device comprising a sensor and afirst camera, wherein the sensor comprises an Electronic Distance Meter(EDM), wherein the measuring device is configured for: from a firstpose: with the sensor, generating a first three-dimensionalrepresentation of a first portion of the object, and with the firstcamera, generating a first image covering at least part of the firstportion of the object, and from a second pose: with the sensor,generating a second three-dimensional representation of a second portionof the object, and with the first camera, generating a second imagecovering at least part of the second portion of the object, a stationaryfirst projector arranged externally with respect to the measuringdevice, and configured for projecting a texture onto both first andsecond portions of the object, a second projector, which is stationaryor comprised by the measuring device; and a stitching computerconfigured for generating a unitary three-dimensional representation ofboth the first and second portions of the object from the first andsecond three-dimensional representations based on the first and secondimages.
 4. The measuring system according to claim 1, wherein thetexture has a non-repetitive pattern.
 5. The measuring system accordingto claim 1, wherein the first projector is configured for projecting thesame texture when the first camera is generating the first and secondimage.
 6. The measuring system according to claim 1, wherein, forgenerating a unitary three-dimensional representation, the stitchingcomputer is configured for matching the first and secondthree-dimensional representations based on the texture as captured inthe first and second images.
 7. The measuring system according claim 1,wherein the first image, the second image, the first three-dimensionalrepresentation, and the second three-dimensional representations have acommon overlap area.
 8. The measuring system according to claim 1,wherein, for generating a unitary three-dimensional representation, thestitching computer is configured for transforming at least one of thefirst and second three-dimensional representations based on matching thetexture as captured in the first image and the texture as captured inthe second image.
 9. The measuring system according to claim 1, whereinthe measuring device is further configured for, from a third pose: withthe sensor, generating a third three-dimensional representation of athird portion of the object, and with the first camera, generating athird image covering at least part of the third portion of the object,and wherein the stitching computer is configured for: generating aunitary three-dimensional representation of the first, second, and thirdportions of the object from the first, second, and thirdthree-dimensional representations based on the third image and at leastone of the first and second image.
 10. A measuring system configured forthree-dimensionally reconstructing a surface geometry of an object, thesystem comprising: a movable measuring device comprising a sensor and afirst camera, wherein the measuring device is configured for: from afirst pose: with the sensor, generating a first three-dimensionalrepresentation of a first portion of the object, and with the firstcamera, generating a first image covering at least part of the firstportion of the object, and from a second pose: with the sensor,generating a second three-dimensional representation of a second portionof the object, and with the first camera, generating a second imagecovering at least part of the second portion of the object, a stationaryfirst projector arranged externally with respect to the measuringdevice, and configured for projecting a texture onto both first andsecond portions of the object, a second projector, which is stationaryor comprised by the measuring device, and a stitching computerconfigured for generating a unitary three-dimensional representation ofboth the first and second portions of the object from the first andsecond three-dimensional representations based on the first and secondimages, wherein the stitching computer is configured for: applying anExpectation-maximisation (EM)-optimisation of the unitarythree-dimensional representation of the first, second, and thirdportions of the object based on the first, second, and third images. 11.The measuring system according to claim 1, wherein the stitchingcomputer is configured for: receiving pose data, wherein the pose datarepresent a chronological sequence of poses of the measuring device, andgenerating the unitary three-dimensional representation based on thepose data.
 12. The measuring system according to claim 1, wherein themeasuring device is configured for generating the pose data.
 13. Themeasuring system according to claim 1, the system comprising:positioning means configured for moving the measuring device, and acontroller configured for controlling the positioning means andproviding the first and second pose as a predetermined pose.
 14. Themeasuring system according claim 1, wherein the stitching computer isconfigured for scaling the three-dimensional representations bydetecting and identifying a known marker in at least one of the firstimage and the second image.
 15. The measuring system according to claim3, wherein, for generating a unitary three-dimensional representation,the stitching computer is configured for matching the first and secondthree-dimensional representations based on the texture as captured inthe first and second images.
 16. The measuring system according to claim3, wherein, for generating a unitary three-dimensional representation,the stitching computer is configured for transforming at least one ofthe first and second three-dimensional representations based on matchingthe texture as captured in the first image and the texture as capturedin the second image.
 17. The measuring system according to claim 3,wherein the measuring device is further configured for, from a thirdpose: with the sensor, generating a third three-dimensionalrepresentation of a third portion of the object, and with the firstcamera, generating a third image covering at least part of the thirdportion of the object, and wherein the stitching computer is configuredfor: generating a unitary three-dimensional representation of the first,second, and third portions of the object from the first, second, andthird three-dimensional representations based on the third image and atleast one of the first and second image.
 18. The measuring systemaccording to claim 10, wherein, for generating a unitarythree-dimensional representation, the stitching computer is configuredfor matching the first and second three-dimensional representationsbased on the texture as captured in the first and second images.
 19. Themeasuring system according to claim 10, wherein, for generating aunitary three-dimensional representation, the stitching computer isconfigured for transforming at least one of the first and secondthree-dimensional representations based on matching the texture ascaptured in the first image and the texture as captured in the secondimage.
 20. The measuring system according to claim 10, wherein themeasuring device is further configured for, from a third pose: with thesensor, generating a third three-dimensional representation of a thirdportion of the object, and with the first camera, generating a thirdimage covering at least part of the third portion of the object, andwherein the stitching computer is configured for: generating a unitarythree-dimensional representation of the first, second, and thirdportions of the object from the first, second, and thirdthree-dimensional representations based on the third image and at leastone of the first and second image.